THE CARNIVOROUS SLUGS OF SOUTH AFRICA. 139 



examined, these two connectives were joined on the right 

 side by a short transverse filament not far from their origin 

 (PI. XV, %. 71). 



The Nerves of the Cerebkal (xANglia. — From each 

 cerebral ganglion arise two large nerves which are as thick 

 as the cerebro-pedal and cerebro-pleural connectives. These 

 are the olfactory nei've to the upper tentacle, and the nerve 

 to the lower tentacle. The olfactory nerve springs from the 

 upper surface of the anterior end of the ganglion, towards 

 the inner side (PI. XV, figs. 70-72). Near its origin there 

 also arise three slender nerves, namely, the two peritentacular 

 nerves, and the optic nerve, which is distinct from the 

 olfactory nerve even from the ganglion. The nerve to the 

 lower tentacle arises nearer the outer edge of the ganglion 

 than the four nerves just described, and external to the 

 accessory lobe. Near it arise the two labial nerves, which 

 are very much narrower than the nerve to the lower tentacle, 

 but not quite so slender as the optic and peritentacular 

 nerves. As in most genera the nerve to the penis also springs 

 from this region in the right cerebral ganglion ; it is of about 

 the same thickness as the labial nerves. Beutler ^ states that 

 in Paryphanta hochstetteri (P/V.) the penial nerve 

 does not arise separately from the cerebral ganglion, but 

 seems to branch from one of the other nerves. On the other 

 hand, in the Streptaxida3^ the nerve to the penis arises 

 directly from the pedal ganglion, instead of its fibres first 

 traversing the right cerebral ganglion, as is usually the case. 

 Near the origin of the sub-cerebral commissure a very 

 slender nerve arises on each side, and runs down with it in 

 the connective tissue on the anterior side of the cerebro-pedal 

 connective. Above this connective, on the dorsal surface of 

 each ganglion, there arises another very slender nerve, which at 

 first goes obliquely backwards, but quickly curves outwards, 

 and runs down to the ventral group of ganglia between 

 the two connectives. This is almost certainly the nervus 



1 Op.cit., p. 400. 



- Wiegmann, F., op. cit., p. 62. 

 VOL. 3, PART 2. 11 



